The term "planar array antenna" used in this application is intended to include resonant and non-resonant slotted arrays excited by a wave guide or micro-strip network and Micro-strip antennas normally formed by micro-strip patches, stubs or dipoles etched in the surface of a metal cladded dielectric substrate. Micro-strip antennas are usually fed via a micro-strip but wave guides or coaxial feeds may also be used. The term "planar array antenna" further includes dielectric resonant antennas excited either by a micro-strip or wave guide network.
The problem of rain wetting antenna particularly planar array antennas used for short wave length transmissions, i.e. transmissions with wavelengths in the millimeter range are well recognized. Water or condensate present on the radiating face of planar array antenna interferes with reception or transmission of these short waves and thereby necessitates the use of much more sophisticated electronics to obtain a meaningful signal from the distorted signal available from the wet antenna. This wetting phenomenon significantly increases the capital and operating cost of these planar array antennas.
A paper by Cheah entitled "Wet Antenna Effect on VSAT Rain Margin" in IEEE Transactions on Communications, Vol. 41, No. 8, August 1993 has described wet antenna effect on VSAT (very small aperture terminal).